"The wardens climbed into their truck, ready to leave. 'You'll need about seven cords of firewood. Concentrate on that. You'll have to get it all in before the snow grounds your truck.'""Though I didn't want to ask, it seemed important. 'What's a cord?'"So begins Pete Fromm's seven winter months alone in a tent in the Selway-Bitterroot Wilderness guarding salmon eggs. After blundering into this forbidding errand as a college lark, Fromm gradually...